The Old Prussian language has always puzzled linguists. While other Baltic languages, such as Lithuanian and Latvian, have remained in use to the present day, Old Prussian was extinguished at the beginning of eighteenth century, and the extant Old Prussian linguistic corpus is quite limited in scope. Drawing on two bilingual vocabularies and three Lutheran Catechisms (as well as onomastic evidence and several other minor texts), this work critically explores the linguistic and historiographical contours of Old Prussian.